Dichroic materials are useful for preferentially transmitting light polarized in one direction relative to light polarized in other directions. When a dichroic material is placed in the path of a beam of randomly polarized light and the component of transmitted light polarized in one plane is of low or negligible luminous flux compared to the luminous flux of light polarized in the orthogonal plane, the transmitted light is said to be linearly polarized, and the layer of dichroic material is referred to as a linear dichroic polarizer. Dichroic polarizers may transmit light of a particular polarization over a relatively wide spectrum, such as the visible spectrum, and may additionally perform a color filtering function by transmitting light of a particular polarization in only limited ranges of wavelengths.
One class of material suitable for producing dichroic effects is the class known as pleochroic dyes. A pleochroic dye molecule is a molecule having a light absorption spectrum that varies as a function of the orientation of the molecule with respect to the polarization of incident light. Dichroic polarizers can be made by forming a layer of oriented pleochroic dye molecules on a substrate. Pleochroic dye molecules that are self-orienting when applied to a suitable substrate are known, as are pleochroic dye molecules which require the application of some other orienting means, such as blending with or otherwise combining with an oriented matrix material in order to produce suitable orientation.
Oriented pleochroic dyes typically transmit light polarized orthogonally to the dye molecule orientation, and absorb all other light, except that light polarized corresponding to the dye molecule orientation and having the color of the dye is transmitted. Since the optical function of most polarizers is to block substantially all light not of the desired polarization, single pleochroic dyes are of limited use as polarizers. More complete polarization can be achieved by incorporating several pleochroic dyes into the polarizer, so as to cover a larger portion of the visible spectrum, thereby producing, for example, a neutral density polarizer. Any desired color filtering can then be provided by a separate color filter.
There currently exists a need for colored polarizers that can transmit light of a specific color and one polarization, and either block substantially all visible light or transmit a different color of light of the other polarization. As described in connection with the present invention, such polarizers can be patterned and used as an improved color filter. Such polarizers can also be used to achieve stylized color effects in reflective, transmissive, or transflective displays.
In an exemplary embodiment, the present invention provides a guest-host polarizer that includes a host matrix and at least a first guest dye and a second guest dye. The first guest dye is disposed in the host matrix and oriented to absorb a first portion of visible light having a first polarization state, and the second guest dye is disposed in the host matrix and oriented to absorb a second portion of visible light having a second polarization state orthogonal to the first polarization state.
In another exemplary embodiment, the present invention provides a transflective liquid crystal display that includes a backlight, a liquid crystal material disposed between a top substrate and a bottom substrate to selectively alter a polarization of light transmitted threrethrough, a transflector disposed between the backlight and the liquid crystal material, a bottom polarizer disposed between the transflector and the liquid crystal material, and a top polarizer positioned adjacent to the top substrate. Either or both of the bottom polarizer and top polarizer includes a guest-host polarizer that has a host matrix, one or more first guest dyes disposed in the host matrix and oriented to absorb a first portion of visible light having a first polarization state, and one or more second guest dyes disposed in the host matrix and oriented to absorb a second portion of visible light having a second polarization state orthogonal to the first polarization state.
In still another exemplary embodiment, the present invention provides a polarizer construction that includes a reflective polarizer and one or more colored dichroic polarizers. The reflective polarizer is disposed on one side of the construction and the colored polarizer(s) is/are disposed on the other side of the construction. The one or more colored dichroic polarizers are arranged so that when the construction is illuminated from the first side, an observer viewing the construction from the second side will observe a first spectral distribution of visible light and when the construction is illuminated from the second side, an observer viewing the construction from the second side will observe a second spectral distribution of visible light different from the first spectral distribution.
In still another exemplary embodiment, the present invention provides a color liquid crystal display that includes a liquid crystal material disposed between two parallel display panel substrates, at least one of the display panel substrates having an array of color filters disposed thereon. At least one of the color filters includes a guest-host polarizer that has a host matrix, one or more first guest dyes disposed in the host matrix and oriented to absorb a first portion of visible light having the first polarization state, and one or more second guest dyes disposed in the host matrix and oriented to absorb a second portion of visible light having the second polarization state orthogonal to the first polarization state.
In another exemplary embodiment, the present invention provides a projector system that includes a projector engine that emits one or more colors of light having one polarization and one or more other colors of light having an orthogonal polarization, a screen disposed to display the light emitted from the projector engine, and a colored polarizer disposed between the screen and the projection engine. The colored polarizer can be arranged to substantially transmit the same colors and polarizations of light emitted by the projector engine so that the intensity of the image produced on the screen is not significantly reduced by the polarizer, while at the same time the polarizer filters ambient light.
In yet another exemplary embodiment, the present invention provides a method for imagewise placement of polarizing elements. The method includes providing a donor element that has a base sheet, a guest-host polarizer transfer layer, and a light-to-heat conversion layer disposed between the base sheet and the guest-host polarizer transfer layer. Next, the transfer layer of the donor element is placed in contact with a receptor substrate and portions of the transfer layer are transferred from the donor element to the receptor substrate by exposing selected areas of the donor element to imaging radiation. Finally, the donor element is removed from the receptor substrate.